The invention relates to a g-force sensitive label for detecting and indicating the application of a g-force, a sample tube for centrifuging biological samples comprising the label, an analytical system and a method for determining the centrifugation status of a sample tube comprising a g-force sensitive label.
Pre-analytical systems (sample sorters, centrifuges, etc.) need to know the centrifugation status of a biological sample in order to determine whether a centrifugation step to separate various sample constituents has already been accomplished or not. An additional, unnecessary centrifugation step applied on a sample tube may have a negative impact on the quality of an analysis performed on that sample. For example, many sample tubes used for preparing plasma or serum from whole blood samples comprise a gel for stably keeping the sediment, which can consist of sedimented cells, a particular sedimented cell fraction, a sedimented clot, and the like, separated from the serum or plasma after the serum or plasma has been separated from the sediment. If one or more additional centrifugation steps are carried out on the already centrifuged sample, the gel barrier may be damaged.
Various approaches to automate the task of detecting whether a biological sample tube has been centrifuged or not have been developed: in many laboratories, an Information Technology system (“IT system”), e.g., a LIS or laboratory middleware, is used to control a laboratory workflow, thereby also keeping track of the current centrifugation status of one or multiple biological samples. However, the amount and type of data managed by a laboratory, which is integrated in the laboratory's IT-system, varies between different laboratories. Many laboratories, in particular smaller ones, currently do not integrate data related to the centrifugation state of the samples.
In many laboratories, the centrifugation status is determined by imaging-systems. Manual as well as image-system based approaches are error prone: in the case of blood samples, for example, a slight separation effect can already be observed when a biological sample is left to stand for one hour or longer. As a consequence, image-system based approaches in many cases will wrongly interpret this naturally occurring separation effect of constituents of various biological samples that have been left to stand for a while as the result of an applied centrifugation step. In particular, whole blood samples derived for preparing plasma or serum samples by applying a centrifugation step show significant sedimentation after just one hour of upright sample tube storing; the upper part of the tube will naturally become transparent. Therefore, an optical detector cannot distinguish reliably between a properly centrifuged sample and a plasma sample with naturally occurring sedimentation.